... Aurora Over Alaska . ... 560 Kilometers Above Europa . ... A Sky Full Of Hydrogen . ... Interstellar space is filled with extremely tenuous clouds of gas which are mostly Hydrogen. ... EGGs, short for evaporating gaseous globules, are dense regions of mostly molecular hydrogen gas that fragment and gravitationally collapse to form stars. ... The orange dot in the above false-color drawing represents the current location of the Sun among local gas clouds in the spiral Milky Way Galaxy. ...